[SCSI] 53c700: Allow setting burst length

This is a patch, which allows not only disabling bursting but to specify
different burst lenghts. This feature is needed to get the 53c700 driver
working for the onboard SCSI controller of SNI RM machines, which only
work reliably with a 4 word burst length.
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/53c700.c

@@ -667,12 +667,30 @@ NCR_700_chip_setup(struct Scsi_Host *host)
 	__u8 min_xferp = (hostdata->chip710 ? NCR_710_MIN_XFERP : NCR_700_MIN_XFERP);
 
 	if(hostdata->chip710) {
-		__u8 burst_disable = hostdata->burst_disable
-			? BURST_DISABLE : 0;
+		__u8 burst_disable = 0;
+		__u8 burst_length = 0;
+
+		switch (hostdata->burst_length) {
+			case 1:
+			        burst_length = BURST_LENGTH_1;
+			        break;
+			case 2:
+			        burst_length = BURST_LENGTH_2;
+			        break;
+			case 4:
+			        burst_length = BURST_LENGTH_4;
+			        break;
+			case 8:
+			        burst_length = BURST_LENGTH_8;
+			        break;
+			default:
+			        burst_disable = BURST_DISABLE;
+			        break;
+		}
 		dcntl_extra = COMPAT_700_MODE;
 
 		NCR_700_writeb(dcntl_extra, host, DCNTL_REG);
-		NCR_700_writeb(BURST_LENGTH_8  | hostdata->dmode_extra,
+		NCR_700_writeb(burst_length | hostdata->dmode_extra,
 			       host, DMODE_710_REG);
 		NCR_700_writeb(burst_disable | (hostdata->differential ? 
 						DIFF : 0), host, CTEST7_REG);

drivers/scsi/53c700.h

@@ -203,7 +203,7 @@ struct NCR_700_Host_Parameters {
 	__u32	force_le_on_be:1;
 #endif
 	__u32	chip710:1;	/* set if really a 710 not 700 */
-	__u32	burst_disable:1;	/* set to 1 to disable 710 bursting */
+	__u32	burst_length:4;	/* set to 0 to disable 710 bursting */
 
 	/* NOTHING BELOW HERE NEEDS ALTERING */
 	__u32	fast:1;		/* if we can alter the SCSI bus clock

drivers/scsi/lasi700.c

@@ -123,6 +123,7 @@ lasi700_probe(struct parisc_device *dev)
 		hostdata->force_le_on_be = 0;
 		hostdata->chip710 = 1;
 		hostdata->dmode_extra = DMODE_FC2;
+		hostdata->burst_length = 8;
 	}
 
 	host = NCR_700_detect(&lasi700_template, hostdata, &dev->dev);

drivers/scsi/sim710.c

@@ -123,6 +123,7 @@ sim710_probe_common(struct device *dev, unsigned long base_addr,
 	hostdata->differential = differential;
 	hostdata->clock = clock;
 	hostdata->chip710 = 1;
+	hostdata->burst_length = 8;
 
 	/* and register the chip */
 	if((host = NCR_700_detect(&sim710_driver_template, hostdata, dev))